Helga Tan Fellow is participating in the greening of the First Coast by cultivating actual greens — and employing a team of fish as her unofficial sharecroppers.

Her farming method is referred to as aquaponics, where koi and plants form a symbiotic relationship that results in a vegetable harvest.

Six months ago, Fellow was inspired to establish GYO Greens, an aquaponic farm and educational center, because of her passion for promoting environmentally sustainable practices.

“I am a big fan of environmental practices, and I love gardening and education, so this seemed like a good fit,” she said.

Fellow, a former engineer in medical device manufacturing who’s spent time as a volunteer in London at the Royal Botanical Gardens in Kew, has a simple mission for GYO Greens: Grow fresh, natural organic vegetables while educating the community about aquaponics farming. Students from Ponte Vedra High School, Landrum and Bolles have visited her farm to learn about the process.

On a recent balmy December day, team member Elia Ballas provided a tour of the facility at 147 Canal Blvd. in Palm Valley. He explained aquaponics, which “focuses on the symbiotic relationship between the fish and the plants.” Two large tanks containing about a thousand fish, mostly koi with some tilapia, are where the cycle begins.

“The waste produced by the fish provides the nutrients for the plants,” said Ballas. “The plants then assist in the filtration of the water which is then returned clean and fresh back to the fish.”

The only cause for adding water to the cycle is evaporation; aquaponics requires up to 80 percent less water than traditional farming methods. According to Ballas, no pesticides or chemicals or fertilizers are used. Plant-sustaining nutrients are produced by the fish. Pest control is achieved through reliance on beneficial insects and companion planting.

At the center, a small pump moves the water from the fish tanks to the plants and back again, with hydrostatic pressure doing most of the work. Ballas calls aquaponics “a smarter version of hydroponics” and said that plants grow 50 percent faster compared to traditional methods of gardening, thanks to the rapid nutrients and increased oxygen supply. The farm is a result of more than four years of research.

Plants are grown in coconut and vermiculite, anchored in “rafts” of high density foam floating on the water from the fish tank. The focus is on avoiding waste as the rafts can be used again and again for years. Mostly recycled materials were used in the building of the facility. Neighbor Tab Baer built the storage, planters, winter covers, parking, harvesting tables and washing areas from construction material placed in waste containers.

GYO Greens has been in operation for six months. The farm is what Fellow refers to as a “young system,” growing a lot of greens. As the system matures, staff will begin growing tomatoes, cucumbers, beans and other crops. For now, they are focusing on the winter-hardy crops including arugula, Swiss chard, spinach and herbs such as cilantro and sage. They also grow onions and edible flowers.

At the center, staff have set up a “seeding table” in order to cultivate seedlings for planting. The system also uses the water system, and about half of the seedlings are Swiss chard. There is also a small section of the seeding table dedicated to “microgreens,” a trendy crop valued for its high concentration of nutrients. They are young seedlings of vegetables harvested about 11 days after germination that contain up to 40 times the vital nutrients compared to mature vegetables.

In addition to providing greens and herbs to local restaurants, GYO Greens allows visitors to pick their own greens. Most are $1 an ounce. All are entirely organic. The owners are looking into cooperating with local delivery services, which will make it easier for Beaches residents to put healthy, organic greens on the table.